Eliminate hardcodings in the PublishingActionsBean

There are several issues in the current publishing mechanism:

• the getSectionsSelectModel() method is using hardcoded reference to the "Domain" document type
• the same method above is using the first domain it founds in the portal, making it impossible to use publishing if one has more than one domain
• there is also a problem with the way the section root and the section are found: right now, these are found using the facelets "MasterPublishSpace" and "PublishSpace". The problem is again when one have many domains, each with it's own type of section roots and sections. The current implementation is assuming that only a document type exists with the "MasterPublishSpace" facelet. Same for "PublishSpace" facelet. There are 2 solution I see: either check only the document types with those facets that exist in the current domain and assume there is only on section root / section document type per domain, or change the API so that the getRootName() and getSectionName() return a list of document types instead of a single String with one document type.